1. Field of the Disclosure
The present invention relates to a turbine engine blade and to a turbine wheel, in particular a low pressure turbine wheel.
2. Description of the Related Art
A turbine wheel conventionally comprises a disk having its radially outer periphery formed with a series of teeth defining between them slots that are used for mounting blades.
Each blade has an airfoil connected by a platform to a middle radial wall extending axially and prolonged radially inwards by a blade root for mounting in a slot of the disk. The platform and said middle wall define two lateral cavities situated on either side of said middle wall and opening out circumferentially for receiving sealing members.
More particularly, the platform of each blade has a main wall in the form of a portion of a cylinder or a portion of a cone, which wall is extended upstream by an upstream radial rim that extends circumferentially, the rim itself being extended at its radially inner end by a lip extending upstream. A rib also extends downstream from the upstream rim, level with the upstream lip, said rib defining upstream bearing surfaces facing radially inwards and situated on either side of the middle wall.
Furthermore, the main wall of the platform forms a lip at its downstream end. A downstream rim extends circumferentially and radially inwards from a downstream zone of the main wall of the platform. The free end of the downstream rim forms downstream bearing surfaces facing radially inwards and situated on either side of the middle wall.
The main wall, the upstream and downstream rims, and the rib of the platform extend laterally on either side of the middle wall of the blade.
A lateral cavity is thus defined on either side of the middle wall by the main wall, by the upstream and downstream rims, by the rib, and by the middle wall.
In the assembled position, the platforms of the blades are arranged circumferentially in adjacent manner and they surround the teeth of the disk. The upstream and downstream bearing surfaces come to bear against the upstream and downstream ends of the corresponding adjacent teeth, with the root of each blade being spaced apart from the bottom of the corresponding slot.
The longitudinal ends of the platforms of the blades are spaced apart from one another in the circumferential direction by small amounts of clearance. Each above-mentioned sealing member is engaged in part in one of the lateral cavities of one blade and in part in the opposite lateral cavity of the directly adjacent blade.
In operation, the above-mentioned sealing members are urged radially outwards by centrifugal force and they come to bear radially against the inside faces of the platforms in order to limit leaks of gas between the longitudinal edges of the platforms. These members may also provide damping of the vibration to which the blades are subjected in operation.
Such a structure is disclosed in particular in Document FR 2 972 759 in the name of the Applicant, and it serves to hold the blades effectively in position in the slots while limiting leaks between the platforms of the blades. Nevertheless, that structure presents relatively great weight, which it would be appropriate to reduce in order to improve the performance of the turbine engine.